Endoluminal vascular prosthesis

ABSTRACT

Disclosed is a tubular endoluminal vascular prosthesis, useful in treating, for example, an abdominal aortic aneurysm. The prosthesis comprises a self expandable wire support structure surrounded by a flexible tubular membrane. A delivery catheter and methods are also disclosed.

This application is a continuation of U. S. application Ser. No.09/034,689 filed on Mar. 4, 1998 now U. S. Pat. No. 6,077,296.

BACKGROUND OF THE INVENTION

The present invention relates to endoluminal vascular prostheses, and,in one application, to self-expanding endoluminal vascular prosthesesfor use in the treatment of abdominal aortic aneurysms.

An abdominal aortic aneurysm is a sac caused by an abnormal dilation ofthe wall of the aorta, a major artery of the body, as it passes throughthe abdomen. The abdomen is that portion of the body which lies betweenthe thorax and the pelvis. It contains a cavity, known as the abdominalcavity, separated by the diaphragm from the thoracic cavity and linedwith a serous membrane, the peritoneum. The aorta is the main trunk, orartery, from which the systemic arterial system proceeds. It arises fromthe left ventricle of the heart, passes upward, bends over and passesdown through the thorax and through the abdomen to about the level ofthe fourth lumbar vertebra, where it divides into the two common iliacarteries.

The aneurysm usually arises in the infrarenal portion of the diseasedaorta, for example, below the kidneys. When left untreated, the aneurysmmay eventually cause rupture of the sac with ensuing fatal hemorrhagingin a very short time. High mortality associated with the rupture ledinitially to transabdominal surgical repair of abdominal aorticaneurysms. Surgery involving the abdominal wall, however, is a majorundertaking with associated high risks. There is considerable mortalityand morbidity associated with this magnitude of surgical intervention,which in essence involves replacing the diseased and aneurysmal segmentof blood vessel with a prosthetic device which typically is a synthetictube, or graft, usually fabricated of Polyester, Urethane, P, DACRON®,TEFLON®, or other suitable material.

To perform the surgical procedure requires exposure of the aorta throughan abdominal incision which can extend from the rib cage to the pubis.The aorta must be closed both above and below the aneurysm, so that theaneurysm can then be opened and the thrombus, or blood clot, andarteriosclerotic debris removed. Small arterial branches from the backwall of the aorta are tied off. The DACRON® tube, or graft, ofapproximately the same size of the normal aorta is sutured in place,thereby replacing the aneurysm. Blood flow is then reestablished throughthe graft. It is necessary to move the intestines in order to get to theback wall of the abdomen prior to clamping off the aorta.

If the surgery is performed prior to rupturing of the abdominal aorticaneurysm, the survival rate of treated patients is markedly higher thanif the surgery is performed after the aneurysm ruptures, although themortality rate is still quite high. If the surgery is performed prior tothe aneurysm rupturing, the mortality rate is typically slightly lessthan 10%. Conventional surgery performed after the rupture of theaneurysm is significantly higher, one study reporting a mortality rateof 66.5%. Although abdominal aortic aneurysms can be detected fromroutine examinations, the patient does not experience any pain from thecondition. Thus, if the patient is not receiving routine examinations,it is possible that the aneurysm will progress to the rupture stage,wherein the mortality rates are significantly higher.

Disadvantages associated with the conventional, prior art surgery, inaddition to the high mortality rate include the extended recovery periodassociated with such surgery; difficulties in suturing the graft, ortube, to the aorta; the loss of the existing aorta wall and thrombosisto support and reinforce the graft; the unsuitability of the surgery formany patients having abdominal aortic aneurysms; and the problemsassociated with performing the surgery on an emergency basis after theaneurysm has ruptured. A patient can expect to spend from one to twoweeks in the hospital after the surgery, a major portion of which isspent in the intensive care unit, and a convalescence period at homefrom two to three months, particularly if the patient has otherillnesses such as heart, lung, liver, and/or kidney disease, in whichcase the hospital stay is also lengthened. Since the graft must besecured, or sutured, to the remaining portion of the aorta, it is manytimes difficult to perform the suturing step because the thrombosispresent on the remaining portion of the aorta, and that remainingportion of the aorta wall may many times be friable, or easily crumbled.

Since many patients having abdominal aortic aneurysms have other chronicillnesses, such as heart, lung, liver, and/or kidney disease, coupledwith the fact that many of these patients are older, the average agebeing approximately 67 years old, these patients are not idealcandidates for such major surgery.

More recently, a significantly less invasive clinical approach toaneurysm repair, known as endovascular grafting, has been developed.Parodi, et al. provide one of the first clinical descriptions of thistherapy. Parodi, J. C., et al., “Transfemoral Intraluminal GraftImplantation for Abdominal Aortic Aneurysms,” 5 Annals of VascularSurgery 491 (1991). Endovascular grafting involves the transluminalplacement of a prosthetic arterial graft in the endoluminal position(within the lumen of the artery). By this method, the graft is attachedto the internal surface of an arterial wall by means of attachmentdevices (expandable stents), typically one above the aneurysm and asecond stent below the aneurysm.

Stents permit fixation of a graft to the internal surface of an arterialwall without sewing or an open surgical procedure. Expansion of radiallyexpandable stents is conventionally accomplished by dilating a balloonat the distal end of a balloon catheter. In U.S. Pat. No. 4,776,337, forexample, Palmaz describes a balloon-expandable stent for endovasculartreatments. Also known are self-expanding stents, such as described inU.S. Pat. No. 4,655,771 to Wallsten.

Notwithstanding the foregoing, there remains a need for a transluminallyimplantable endovascular prosthesis, such as for spanning an abdominalaortic aneurysm. Preferably, the tubular prosthesis can be self expandedat the site to treat the abdominal aortic aneurysm.

SUMMARY OF THE INVENTION

There is provided in accordance with one aspect of the present inventionan endoluminal prosthesis. The endoluminal prosthesis comprises atubular wire support having a proximal end, a distal end and centrallumen extending therethrough. The wire support comprises at least afirst and a second axially adjacent tubular segments, joined by aconnector extending therebetween. The first and second segments and theconnector are formed from a single length of wire.

In one embodiment, the wire in each segment comprises a series ofproximal bends, a series of distal bends, and a series of wall (strut)segments connecting the proximal bends and distal bends to form atubular segment wall. Preferably, at least one proximal bend on a firstsegment is connected to at least one corresponding distal bend on asecond segment. The connection may be provided by a metal link, asuture, or other connection means known in the art.

Preferably, the endoluminal prosthesis further comprises a polymericlayer such as a tubular PTFE sleeve, on the support.

In accordance with another aspect of the present invention, there isprovided a method of making an endoluminal prosthesis. The methodcomprises the steps of providing a length of wire, and forming the wireinto two or more zig zag sections, each zig zag section connected by alink. The formed wire is thereafter rolled about an axis to produce aseries of tubular elements positioned along the axis such that eachtubular element is connected to the adjacent tubular element by a link.Preferably, the method further comprises the step of positioning atubular polymeric sleeve concentrically on at least a portion of theendoluminal prosthesis.

In accordance with another aspect of the present invention, there isprovided a multizone endoluminal prosthesis. The multizone prosthesiscomprises a tubular wire support having a proximal end, a distal end anda central lumen extending therethrough. The wire support comprises atleast a first and a second axially adjacent tubular segments, joined bya connector extending therebetween. The first tubular segment has adifferent radial strength than the second tubular segment. In oneembodiment, the prosthesis further comprises a third tubular segment. Atleast one of the tubular segments has a different radial strength thanthe other two tubular segments. In another embodiment, a proximal end ofthe prosthesis is self expandable to a greater diameter than a centralregion of the prosthesis.

In accordance with another aspect of the present invention, there isprovided an endoluminal prosthesis. The prosthesis comprises an elongateflexible wire, formed into a plurality of axially adjacent tubularsegments spaced along an axis. Each tubular segment comprises a zig zagsection of wire, having a plurality of proximal bends and distal bends,with the wire continuing between each adjacent tubular segment creatingan integral structural support system throughout the longitudinal lengthof the device. The prosthesis is radially collapsible into a first,reduced cross sectional configuration for implantation into a bodylumen, and self expandable to a second, enlarged cross sectionalconfiguration at a treatment site in a body lumen.

Preferably, the prosthesis further comprises an outer tubular sleevesurrounding at least a portion of the prosthesis. One or more lateralperfusion ports may be provided through the tubular sleeve.

In one embodiment, the prosthesis has an expansion ratio of at leastabout 1:5, and, preferably at least about 1:6. The prosthesis in anotherembodiment has an expanded diameter of at least about 20 mm in anunconstrained expansion, and the prosthesis is implantable using acatheter no greater than about 16 French. Preferably, the prosthesis hasan expanded diameter of at least about 25 mm, and is implantable on adelivery device having a diameter of no more than about 16 French.

In accordance with a further aspect of the present invention, there isprovided a method of implanting an endoluminal vascular prosthesis. Themethod comprises the steps of providing a self expandable endoluminalvascular prosthesis, having a proximal end, a distal end, and a centrallumen extending therethrough. The prosthesis is expandable from a first,reduced diameter to a second, enlarged diameter. The prosthesis ismounted on a catheter, such that when the prosthesis is in the reduceddiameter configuration on the catheter, the catheter diameter throughthe prosthesis is no more than about 16 French. The catheter isthereafter introduced into the body lumen and positioned such that theprosthesis is at a treatment site in the body lumen. The prosthesis isreleased at the treatment site, such that it expands from the firstdiameter to the second diameter, wherein the second diameter is at leastabout 20 mm.

Further features and advantages of the present invention will becomeapparent to those of ordinary skill in the art in view of the disclosureherein, when considered together with the attached drawings and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of an endoluminal vascularprosthesis in accordance with the present invention, positioned within asymmetric abdominal aortic aneurysm.

FIG. 2 is an exploded view of an endoluminal vascular prosthesis inaccordance with the present invention, showing a self expandable wiresupport structure separated from an outer tubular sleeve.

FIG. 3 is a plan view of a formed wire useful for rolling about an axisinto a multi-segment support structure in accordance with the presentinvention.

FIG. 4 is an enlarged detail view of a portion of the formed wireillustrated in FIG. 3.

FIG. 5 is a cross sectional view taken along the lines 5—5 of FIG. 4.

FIG. 6 is an alternate cross sectional view taken along the lines 5—5 ofFIG. 4.

FIG. 7 is a fragmentary view of an alternate wire layout in accordancewith a further aspect of the present invention.

FIG. 8 is an elevational view of a crosslinked wire layout in accordancewith the present invention.

FIG. 8A is a plan view of a formed wire layout useful for forming thecrosslinked embodiment of FIG. 8.

FIG. 9 is a fragmentary view of an alternate wire layout in accordancewith a further aspect of the present invention.

FIG. 10 is a fragmentary view of an alternate wire layout in accordancewith a further aspect of the present invention.

FIG. 11 is a fragmentary view of an apex in accordance with one aspectof the present invention.

FIG. 12 is a fragmentary view of an alternate embodiment of an apex inaccordance with the present invention.

FIG. 13 is a further embodiment of an apex in accordance with thepresent invention.

FIG. 14 is a fragmentary view of a further wire layout in accordancewith the present invention.

FIG. 15 is a fragmentary view of a further wire layout in accordancewith the present invention.

FIG. 16 is a fragmentary view of a further wire layout in accordancewith the present invention.

FIG. 17 is a schematic illustration of a delivery catheter in accordancewith the present invention, positioned within an abdominal aorticaneurysm.

FIG. 18 is an illustration as in FIG. 17, with the endoluminalprosthesis partially deployed from the delivery catheter.

FIG. 19 is a cross sectional view taken along the lines 19—19 of FIG.17.

FIG. 20 is a detailed fragmentary view of a tapered wire embodiment inaccordance with a further aspect of the present invention.

FIG. 21 is a schematic representation of the abdominal aortic anatomy,with an endoluminal vascular prosthesis of the present inventionpositioned within each of the right renal artery and the right commoniliac.

FIG. 22 is a modified embodiment of the prosthesis in accordance withthe present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 1, there is disclosed a schematic representation ofthe abdominal part of the aorta and its principal branches. Inparticular, the abdominal aorta 30 is characterized by a right renalartery 32 and left renal artery 34. The large terminal branches of theaorta are the right and left common iliac arteries 36 and 38. Additionalvessels (e.g., second lumbar, testicular, inferior mesenteric, middlesacral) have been omitted for simplification. A generally symmetricalaneurysm 40 is illustrated in the infrarenal portion of the diseasedaorta. An expanded endoluminal vascular prosthesis 42, in accordancewith the present invention, is illustrated spanning the aneurysm 40.Although features of the endoluminal vascular prosthesis of the presentinvention can be modified for use in a bifurcation aneurysm, such as thecommon iliac bifurcation, the endoluminal prosthesis of the presentinvention will be described herein primarily in terms of its applicationin the straight segment of the abdominal aorta, or Thoracic or iliacarteries.

The endoluminal vascular prosthesis 42 includes a polymeric sleeve 44and a tubular wire support 46, which are illustrated in situ in FIG. 1.The sleeve 44 and wire support 46 are more readily visualized in theexploded view shown in FIG. 2. The endoluminal prosthesis 42 illustratedand described herein depicts an embodiment in which the polymeric sleeve44 is situated concentrically outside of the tubular wire support 46.However, other embodiments may include a sleeve situated insteadconcentrically inside the wire support or on both of the inside and theoutside of the wire support. Alternatively, the wire support may beembedded within a polymeric matrix which makes up the sleeve. Regardlessof whether the sleeve 44 is inside or outside the wire support 46, thesleeve may be attached to the wire support by any of a variety of means,including laser bonding, adhesives, clips, sutures, dipping or sprayingor others, depending upon the composition of the sleeve 44 and overallgraft design.

The polymeric sleeve 44 may be formed from any of a variety of syntheticpolymeric materials, or combinations thereof, including PTFE, PE, PET,Urethane, Dacron, nylon, polyester or woven textiles. Preferably, thesleeve material exhibits relatively low inherent elasticity, or lowelasticity out to the intended enlarged diameter of the wire cage 46.The sleeve material preferably has a thin profile, such as no largerthan about 0.002 inches to about 0.005 inches.

In a preferred embodiment of the invention, the material of sleeve 44 issufficiently porous to permit ingrowth of endothelial cells, therebyproviding more secure anchorage of the prosthesis and potentiallyreducing flow resistance, sheer forces, and leakage of blood around theprosthesis. Porosity in polymeric sleeve materials may be estimated bymeasuring water permeability as a function of hydrostatic pressure,which will preferably range from about 3 to 6 psi.

The porosity characteristics of the polymeric sleeve 44 may be eitherhomogeneous throughout the axial length of the prosthesis 42, or mayvary according to the axial position along the prosthesis 42. Forexample, referring to FIGS. 1 and 2, different physical properties willbe called upon at different axial positions along the prosthesis 42 inuse. At least a proximal portion 55 and a distal portion 59 of theprosthesis 42 will seat against the native vessel wall, proximally anddistally of the aneurysm. In these proximal and distal portions, theprosthesis preferably encourages endothelial growth, or, at least,permits endothelial growth to infiltrate portions of the prosthesis inorder to enhance anchoring and minimize leakage. A central portion 57 ofthe prosthesis spans the aneurysm, and anchoring is less of an issue.Instead, minimizing blood flow through the prosthesis wall becomes aprimary objective. Thus, in a central zone 57 of the prosthesis 42, thepolymeric sleeve 44 may either be nonporous, or provided with pores ofno greater than about 60% to 80%.

A multi-zoned prosthesis 42 may also be provided in accordance with thepresent invention by positioning a tubular sleeve 44 on a centralportion 57 of the prosthesis, such that it spans the aneurysm to betreated, but leaving a proximal attachment zone 55 and a distalattachment zone 59 of the prosthesis 42 having exposed wires from thewire support 46. In this embodiment, the exposed wires 46 are positionedin contact with the vessel wall both proximally and distally of theaneurysm, such that the wire, over time, becomes embedded in cell growthon the interior surface of the vessel wall.

In one embodiment of the prosthesis 42, the sleeve 44 and/or the wiresupport 46 is tapered, having a relatively larger expanded diameter atthe proximal end 50 compared to the distal end 52. The tapered designmay allow the prosthesis to conform better to the natural decreasingdistal cross section of the vessel, to reduce the risk of graftmigration and potentially create better flow dynamics.

The tubular wire support 46 is preferably formed from a continuoussingle length of round (shown in FIG. 5) or flattened (shown in FIG. 6)wire. The wire support 46 is preferably formed in a plurality ofdiscrete segments 54, connected together and oriented about a commonaxis. Each pair of adjacent segments 54 is connected by a connector 66as will be discussed. The connectors 66 collectively produce a generallyaxially extending backbone which adds axial strength to the prosthesis42. Adjacent segments can be connected both by the backbone, as well asby other structures, including circumferentially extending sutures 56(illustrated in FIGS. 1 and 2), solder joints, wire loops and any of avariety of interlocking relationships. The suture can be made from anyof a variety of biocompatible polymeric materials or alloys, such asnylon, polypropylene, or stainless steel. Other means of securing thesegments 54 to one another are discussed below (see FIG. 8).

The segmented configuration of the tubular wire support 46 facilitates agreat deal of flexibility. Each segment 54, though joined to adjacentsegments, may be independently engineered to yield desired parameters.Each segment may range in axial length from about 0.3 to about 5 cm.Generally, the shorter their length the greater the radial strength. Anendoluminal prosthesis may include from about 1 to about 50 segments,preferably from about 3 to about 10 segments. For example, while a shortgraft patch, in accordance with the invention, may comprise only 2segments and span a total of 2 to 3 cm, a complete graft may comprise 4or more segments and span the entire aortic aneurysm. In addition to theflexibility and other functional benefits available through employmentof different length segments, further flexibility can be achievedthrough adjustments in the number, angle, or configuration of the wirebends associated with the tubular support. Potential bend configurationsare discussed in greater detail below (see FIGS. 4-16).

A variety of additional advantages can be achieved through themulti-segment configuration of the present invention. For example,referring to FIG. 2, the wire cage 46 is dividable into a proximal zone55, a central zone 57 and a distal zone 59. As has been discussed, thewire cage 46 can be configured to taper from a relatively largerdiameter in the proximal zone 55 to a relatively smaller diameter in thedistal zone 59. In addition, the wire cage 46 can have a transitionaltapered and or stepped diameter within a given zone.

The cage 46 can also be provided with a proximal zone 55 and distal zone59 that have a larger relative expanded diameter than the central zone57, as illustrated in FIG. 2. This configuration may desirably resistmigration of the prosthesis within the vessel. The proximal zone 55and/or distal zone 59 can be left without an outer covering 44, with theouter sleeve 44 covering only the central zone 57. This permits theproximal and distal zones 55, 59 to be in direct contact with tissueproximally and distal to the lesion, which may facilitate endothelialcell growth.

In addition to having differing expanded diameters in different zones ofthe prosthesis 42, different zones can be provided with a differentradial expansion force, such as ranging from about 0.2 lbs to about 0.8lbs. In one embodiment, the proximal zone 55 is provided with a greaterradial force than the central zone 57 and/or distal zone 59. The greaterradial force can be provided in any of a variety of manners discussedelsewhere herein, such as through the use of an additional one or two orthree or more proximal bends 60, distal bends 62 and wall sections 64compared to a reference segment 54 in the central zone 57 or distal zone59. Alternatively, additional spring force can be achieved in theproximal zone 55 through the use of the same number of proximal bends 60as in the rest of the prosthesis, but with a heavier gauge wire. Radialforce beyond the expanded diameter limit of the central zone 57 can beachieved by tightening the suture 56 as illustrated in FIG. 2 such thatthe central zone 57 is retained under compression even in the expandedconfiguration. By omitting a suture at the proximal end and/or distalend of the prosthesis, the proximal end and distal end will flairradially outwardly to a fully expanded configuration as illustrated inFIG. 2.

The wire may be made from any of a variety of different alloys, such aselgiloy, nitinol or MP35N, or other alloys which include nickel,titanium, tantalum, or stainless steel, high Co—Cr alloys or othertemperature sensitive materials. For example, an alloy comprising Ni15%, Co 40%, Cr 20%, Mo 7% and balance Fe may be used. The tensilestrength of suitable wire is generally above about 300 K psi and oftenbetween about 300 and about 340 K psi for many embodiments. In oneembodiment, a Chromium-Nickel-Molybdenum alloy such as that marketedunder the name Conichrom (Fort Wayne Metals, Indiana) has a tensilestrength ranging from 300 to 320 K psi, elongation of 3.5-4.0% andbreaking load at approximately 80 lbs to 70 lbs. The wire may be treatedwith a plasma coating and be provided with/without coating such as:PTFE, Teflon, Perlyne and Drugs.

In addition to segment length and bend configuration, discussed above,another determinant of radial strength is wire gauge. The radialstrength, measured at 50% of the collapsed profile, preferably rangesfrom about 0.2 lb to 0.8 lb, and generally from about 0.4 lb to about0.5 lb. or more. Preferred wire diameters in accordance with the presentinvention, range from about 0.004 inches to about 0.020 inches. Morepreferably, the wire diameters range from about 0.006 inches to about0.018 inches. In general, the greater the wire diameter, the greater theradial strength for a given wire layout. Thus, the wire gauge can bevaried depending upon the application of the finished graft, incombination with/or separate from variation in other design parameters(such as the number of struts, or proximal bends 60 and distal bends 62per segment), as will be discussed. A wire diameter of approximately0.018 inches may be useful in a graft having four segments each having2.5 cm length per segment, each segment having six struts intended foruse in the aorta, while a smaller diameter such as 0.006 inches might beuseful for a 0.5 cm segment graft having 5 struts per segment intendedfor the iliac artery. The length of cage 42 could be as long as about 28cm.

In one embodiment of the present invention, the wire diameter is taperedfrom the proximal to distal ends. Alternatively, the wire diameter maybe tapered incrementally or stepped down, or stepped up, depending onthe radial strength requirements of each particular clinicalapplication. In one embodiment, intended for the abdominal aorticartery, the wire has a cross section of about 0.018 inches in theproximal zone 55 and the wire tapers down to a diameter of about 0.006inches in the distal zone 59 of the graft 42. End point dimensions andrates of taper can be varied widely, within the spirit of the presentinvention, depending upon the desired clinical performance.

Referring to FIG. 3, there is illustrated a plan view of the singleformed wire used for rolling about a longitudinal axis to produce a foursegment tubular wire support. The formed wire exhibits distinctsegments, each corresponding to an individual tubular segment 54 in thetubular support (see FIGS. 1 and 2).

Each segment has a repeating pattern of proximal bends 60 connected tocorresponding distal bends 62 by wall sections 64 which extend in agenerally zig zag configuration when the segment 54 is radiallyexpanded. Each segment 54 is connected to the adjacent segment 54through a connector 66, except at the terminal ends of the graft. Theconnector 66 in the illustrated embodiment comprises two wall sections64 which connect a proximal bend 60 on a first segment 54 with a distalbend 62 on a second, adjacent segment 54. The connector 66 mayadditionally be provided with a connector bend 68, which may be used toimpart increased radial strength to the graft and/or provide a tie sitefor a circumferentially extending suture.

Referring to FIG. 4, there is shown an enlarged view of the wire supportillustrating a connector 66 portion between adjacent segments 54. In theembodiment shown in FIG. 4, a proximal bend 60 comprises about a 180degree arc, having a radial diameter of (w) (Ranging from 0.070 to 0.009inches), depending on wire diameter followed by a relatively shortlength of parallel wire spanning an axial distance of d1. The parallelwires thereafter diverge outwardly from one another and form the strutsections 64, or the proximal half of a connector 66. At the distal endof the strut sections 64, the wire forms a distal bend 62, preferablyhaving identical characteristics as the proximal bend 60, except beingconcave in the opposite direction. The axial direction component of thedistance between the apices of the corresponding proximal and distalbends 60, 62 is referred to as (d) and represents the axial length ofthat segment. The total expanded angle defined by the bend 60 and thedivergent strut sections 64 is represented by α. Upon compression to acollapsed state, such as when the graft is within the deploymentcatheter, the angle α is reduced to α′. In the expanded configuration, αis generally within the range of from about 35° to about 45°. Theexpanded circumferential distance between any two adjacent distal bends62 (or proximal bends 60) is defined as (s).

In general, the diameter W of each proximal bend 60 or distal bend 62 iswithin the range of from about 0.009 inches to about 0.070 inchesdepending upon the wire diameter. Diameter W is preferably as small aspossible for a given wire diameter and wire characteristics. As will beappreciated by those of skill in the art, as the distance W is reducedto approach two times the cross section of the wire, the bend 60 or 62will exceed the elastic limit of the wire, and radial strength of thefinished segment will be lost. Determination of a minimum value for W,in the context of a particular wire diameter and wire material, can bereadily determined through routine experimentation by those of skill inthe art. Similarly, although at least some distance of d1 is desired,from the apex to the first bend in the wall section 64, the distance d1is preferably minimized within the desired radial strength performancerequirements. As d1 increases, it may disadvantageously increase thecollapsed profile of the graft.

As will be appreciated from FIGS. 3 and 4, the sum of the distances (s)in a plane transverse to the longitudinal axis of the finished graftwill correspond to the circumference of the finished graft in thatplane. For a given circumference, the number of proximal bends 60 ordistal bends 62 is directly related to the distance (s) in thecorresponding plane. Preferably, the finished graft in any singletransverse plane will have from about 3 to about 10 (s) dimensions,preferably from about 4 to about 8 (s) dimensions and, more preferably,about 5 or 6 (s) dimensions for an aortic application. Each (s)dimension corresponds to the distance between any two adjacent bends60—60 or 62—62 as will be apparent from the discussion herein. Eachsegment 54 can thus be visualized as a series of triangles extendingcircumferentially around the axis of the graft, defined by a proximalbend 60 and two distal bends 62 or the reverse.

By modifying wire support parameters (such as d, d1, s, alpha andalpha′), the manufacturer enjoys tremendous design control with respectto the total axial length, axial and radial flexibility, radial forceand expansion ratios, and consequently prosthesis performance. Forexample, an increase in the dimension (w) translates directly into anincreased collapsed profile since the circumference of the collapsedprofile can be no smaller than the sum of the distances (w) in a giventransverse plane. Similarly, an increase in the number of proximal bends60 in a given segment may increase radial strength, but will similarlyincrease the collapsed profile. Since the primary radial force comesfrom the proximal bends 60 and distal bends 62, the wall sections 64 actas a lever arm for translating that force into radial strength. As aconsequence, decreasing the length of strut sections 64 for a givennumber of proximal bends 60 will increase the radial strength of thesegment but call for additional segments to maintain overall graftlength. Where a minimal entry profile is desired, radial strength isbest accomplished by decreasing the length of wall sections 64 ratherthan increasing the number of proximal bends 60. On the other hand,increasing the number of (shorter) segments 54 in a given overall lengthgraft will increase the degree of axial shortening upon radial expansionof the graft. Thus, in an embodiment where axial shortening is to beavoided, increased radial strength may be optimized through selection ofwire material or wire gauge and other parameters, while minimizing thenumber of total segments in the graft. Other geometry consequences ofthe present invention will be apparent to those of skill in the art inview of the disclosure herein.

In one embodiment of the type illustrated in FIG. 8A, w is about 2.0mm±1 mm for a 0.018 inch wire diameter. D1 is about 3 mm±1 mm, d isabout 20 mm±1 mm, c is about 23 mm±1 mm, g is about 17 mm,±1 mm, a isabout 3 mm±1 mm and b is about 3 mm±1 mm. Specific dimensions for all ofthe foregoing variables can be varied considerably, depending upon thedesired wire configuration, in view of the disclosure herein.

Referring to FIG. 7, there is shown an alternative wire layout having aplurality of radiussed bends 70 in one or more sections of strut 64which may be included to provide additional flex points to provideenhanced fluid dynamic characteristics and maintain the tubular shape.

In another embodiment of the wire support, illustrated in FIG. 8, eachpair of adjacent proximal and distal segments, 76 and 78, may be joinedby crosslinking of the corresponding proximal and distal bends. Thus, aproximal bend 60 from a distal segment 78 is connected to thecorresponding distal bend 62 of a proximal segment 76, thereby couplingthe proximal segment 76 and distal segment 78. The connection betweencorresponding proximal bends 60 and distal bends 62 can be accomplishedin any of a variety of ways as will be apparent to those of skill in theart in view of the disclosure herein. In the illustrated embodiment, theconnection is accomplished through the use of a link 72. Link 72 may bea loop of metal such as stainless steel, a suture, a welded joint orother type of connection. Preferably, link 72 comprises a metal loop orring which permits pivotable movement of a proximal segment 76 withrespect to a distal segment 78.

In one example of an endoluminal vascular prosthesis in accordance withthe present invention, the proximal segment 76 is provided with sixdistal bends 62. The corresponding distal segment 78 is provided withsix proximal bends 60 such that a one to one correspondence exists. Alink 72 may be provided at each pair of corresponding bends 60, 62, suchthat six links 72 exist in a plane transverse to the longitudinal axisof the graft at the interface between the proximal segment 76 and thedistal segment 78. Alternatively, links 72 can be provided at less thanall of the corresponding bends, such as at every other bend, every thirdbend, or only on opposing sides of the graft. The distribution of thelinks 72 in any given embodiment can be selected to optimize the desiredflexibility characteristics and other performance criteria in a givendesign.

The use of connectors such as cross link 72 enables improved tracking ofthe graft around curved sections of the vessel. In particular, the wirecage 46 as illustrated in FIG. 8 can be bent around a gentle curve, suchthat it will both retain the curved configuration and retain patency ofthe central lumen extending axially therethrough. The embodimentillustrated in FIG. 2 may be more difficult to track curved anatomywhile maintaining full patency of the central lumen. The ability tomaintain full patency while extending around a curve may be desirable incertain anatomies, such as where the aorta fails to follow the linearinfrarenal path illustrated in FIG. 1.

Referring to FIG. 8a, there is illustrated a plan view of a formed wireuseful for rolling about an axis to produce a multi-segmented supportstructure of the type illustrated in FIG. 8. In general, the formed wireof FIG. 8a is similar to that illustrated in FIG. 3. However, whereasany given pair of corresponding distal bends 62 and proximal bends 60 ofthe embodiment of FIG. 3 overlap in the axial direction to facilitatethreading a circumferential suture therethrough, the correspondingdistal bend 62 and proximal bend 60 of the embodiment illustrated inFIG. 8a may abut end to end against each other or near each other asillustrated in FIG. 8 to receive a connector 72 thereon.

The appropriate axial positioning of a distal bend 62 with respect to acorresponding proximal bend 60 can be accomplished in a variety of ways,most conveniently by appropriate formation of the connector bend 68between adjacent segments of the wire cage.

FIGS. 9-16 illustrate alternative bend configurations in accordance withthe present invention. FIG. 9 shows one embodiment having the proximaland distal bends as eyelets, but the connector bend 68, remaining in theusual configuration. The embodiment illustrated in FIG. 10 has theproximal and distal bends as well as the connector bend in the eyeletconfiguration. Various eyelet designs in accordance with the presentinvention are shown in greater detail in FIGS. 11-13, including adouble-looped circular eyelet (FIG. 11), a double-looped triangulareyelet (FIG. 12), and a single-looped triangular eyelet (FIG. 13). Theeyelets can be used to receive a circumferentially extending suture orwire as has been described.

Additional embodiments of the wire configuration are illustrated inFIGS. 14-16. FIG. 14 shows an embodiment of the proximal 60 and distal62 bends in which double bends are employed to increase the flexion.Alternatively, FIG. 15 shows triangular bends having a more pronouncedlength (d1) of parallel wire, and accordingly shorter wall sections 64.Another embodiment of the proximal and distal bends is shown in FIG. 16,wherein the triangular bends include additional flexion points in theform of wall segment bends 70.

Referring to FIGS. 17 and 18, a deployment device and method inaccordance with a preferred embodiment of the present invention areillustrated. A delivery catheter 80, having a dilator tip 82, isadvanced along guidewire 84 until the (anatomically) proximal end 50 ofthe collapsed endoluminal vascular prosthesis 86 is positioned betweenthe renal arteries 32 and 34 and the aneurysm 40. The collapsedprosthesis in accordance with the present invention has a diameter inthe range of about 2 to about 10 mm. Preferably, the diameter of thecollapsed prosthesis is in the range of about 3 to 6 mm (12 to 18French). More preferably, the delivery catheter including the prosthesiswill be 16 F, or 15 F or 14 F or smaller.

The prosthesis 86 is maintained in its collapsed configuration by therestraining walls of the tubular delivery catheter 80, such that removalof this restraint would allow the prosthesis to self expand. Radiopaquemarker material may be incorporated into the delivery catheter 80,and/or the prosthesis 86, at least at both the proximal and distal ends,to facilitate monitoring of prosthesis position. The dilator tip 82 isbonded to an internal catheter core 92, as illustrated in FIG. 18,wherein the internal catheter core 92 and the partially expandedprosthesis 88 are revealed as the outer sheath of the delivery catheter80 is retracted. The internal catheter core 92 is also depicted in thecross-sectional view in FIG. 19.

As the outer sheath is retracted, the collapsed prosthesis 86 remainssubstantially fixed axially relative to the internal catheter core 92and consequently, self-expands at a predetermined vascular site asillustrated in FIG. 18. Continued retraction of the outer sheath resultsin complete deployment of the graft. After deployment, the expandedendoluminal vascular prosthesis has radially self-expanded to a diameteranywhere in the range of about 20 to 40 mm, corresponding to expansionratios of about 1:2 to 1:20. In a preferred embodiment, the expansionratios range from about 1:4 to 1:8, more preferably from about 1:4 to1:6.

In addition to, or in place of, the outer sheath described above, theprosthesis 86 may be maintained in its collapsed configuration by arestraining lace, which may be woven through the prosthesis or wrappedaround the outside of the prosthesis in the collapsed reduced diameter.Following placement of the prosthesis at the treatment site, the lacecan be proximally retracted from the prosthesis thereby releasing it toself expand at the treatment site. The lace may comprise any of avariety of materials, such as sutures, strips of PTFE, FEP, polyesterfiber, and others as will be apparent to those of skill in the art inview of the disclosure herein. The restraining lace may extendproximally through a lumen in the delivery catheter or outside of thecatheter to a proximal control. The control may be a pull tab or ring,rotatable reel, slider switch or other structure for permitting proximalretraction of the lace. The lace may extend continuously throughout thelength of the catheter, or may be joined to another axially moveableelement such as a pull wire.

In general, the expanded diameter of the graft in accordance with thepresent invention can be any diameter useful for the intended lumen orhollow organ in which the graft is to be deployed. For most arterialvascular applications, the expanded size will be within the range offrom about 10 to about 40 mm. Abdominal aortic applications willgenerally require a graft having an expanded diameter within the rangeof from about 20 to about 28 mm, and, for example, a graft on the orderof about 45 mm may be useful in the thoracic artery. The foregoingdimensions refer to the expanded size of the graft in an unconstrainedconfiguration, such as on the table. In general, the graft will bepositioned within an artery having a slightly smaller interior crosssection than the expanded size of the graft. This enables the graft tomaintain a slight positive pressure against the wall of the artery, toassist in retention of the graft during the period of time prior toendothelialization of the polymeric sleeve 44.

The radial force exerted by the proximal segment 94 of the prosthesisagainst the walls of the aorta 30 provides a seal against the leakage ofblood around the vascular prosthesis and tends to prevent axialmigration of the deployed prosthesis. As discussed above, this radialforce can be modified as required through manipulation of various designparameters, including the axial length of the segment and the bendconfigurations. In another embodiment of the present invention, radialtension can be enhanced at the proximal, upstream end by changes in thewire gauge as illustrated in FIG. 20. Note that the wire gauge increasesprogressively along the wall segments 64 from T1 at the proximal bends60 to T2 at the distal bends 62. Consequently, the radial flex exertedby the distal bends 62 is greater than that exerted by the proximalbends 60 and the radial tension is thereby increased at the proximal end50 of the prosthesis. T1 may range from about 0.001 to 0.01 incheswhereas T2 may range from about 0.01 to 0.03 inches.

An alternative embodiment of the wire layout which would cause theradial tension to progressively decrease from the proximal segments tothe distal segments, involves a progressive or step-wise decrease in thewire gauge throughout the entire wire support, from about 0.01 to 0.03inches at the proximal end to about 0.002 to 0.01 inches at the distalend. Such an embodiment, may be used to create a tapered prosthesis.Alternatively, the wire gauge may be thicker at both the proximal anddistal ends, in order to insure greater radial tension and thus, sealingcapacity. Thus, for instance, the wire gauge in the proximal and distalsegments may about 0.01 to 0.03 inches, whereas the intervening segmentsmay be constructed of thinner wire, in the range of about 0.001 to 0.01inches.

Referring to FIG. 21, there is illustrated two alternative deploymentsites for the endoluminal vascular prosthesis 42 of the presentinvention. For example, a symmetrical aneurysm 33 is illustrated in theright renal artery 32. An expanded endoluminal vascular prosthesis 42,in accordance with the present invention, is illustrated spanning thataneurysm 33. Similarly, an aneurysm of the right common iliac 37 isshown, with a prosthesis 42 deployed to span the iliac aneurysm 37.

Referring to FIG. 22, there is illustrated a modified embodiment of theendovascular prosthesis 96 in accordance with the present invention. Inthe embodiment illustrated in FIG. 22, the endovascular prosthesis 96 isprovided with a wire cage 46 having six axially aligned segments 54. Aswith the previous embodiments, however, the endovascular prosthesis 96may be provided with anywhere from about 2 to about 10 or more axiallyspaced or adjacent segments 54, depending upon the clinical performanceobjectives of the particular embodiment.

The wire support 46 is provided with a tubular polymeric sleeve 44 ashas been discussed. In the present embodiment, however, one or morelateral perfusion ports or openings are provided in the polymeric sleeve44, such as a right renal artery perfusion port 98 and a left renalartery perfusion port 100 as illustrated.

Perfusion ports in the polymeric sleeve 44 may be desirable inembodiments of the endovascular prosthesis 96 in a variety of clinicalcontexts. For example, although FIGS. 1 and 22 illustrate a generallysymmetrical aneurysm 40 positioned within a linear infrarenal portion ofthe abdominal aorta, spaced axially apart both from bilaterallysymmetrical right and left renal arteries and bilaterally symmetricalright and left common iliacs, both the position and symmetry of theaneurysm 40 as well as the layout of the abdominal aortic architecturemay differ significantly from patient to patient. As a consequence, theendovascular prosthesis 96 may need to extend across one or both of therenal arteries in order to adequately anchor the endovascular prosthesis96 and/or span the aneurysm 40. The provision of one or more lateralperfusion ports enables the endovascular prosthesis 96 to span the renalarteries while permitting perfusion therethrough, thereby preventing“stent jailing” of the renals. Lateral perfusion through theendovascular prosthesis 96 may also be provided, if desired, for avariety of other arteries including the second lumbar, testicular,inferior mesenteric, middle sacral, and alike as will be well understoodto those of skill in the art.

The endovascular prosthesis 96 is preferably provided with at least one,and preferably two or more radiopaque markers, to facilitate properpositioning of the prosthesis 96 within the artery. In an embodimenthaving perfusion ports 98 and 100 such as in the illustrated design, theprosthesis 96 should be properly aligned both axially and rotationally,thereby requiring the ability to visualize both the axial and rotationalposition of the device. Alternatively, provided that the deliverycatheter design exhibits sufficient torque transmission, the rotationalorientation of the graft maybe coordinated with an indexed marker on theproximal end of the catheter, so that the catheter may be rotated anddetermined by an external indicium of rotational orientation to beappropriately aligned with the right and left renal arteries.

In an alternative embodiment, the polymeric sleeve 44 extends across theaneurysm 40, but terminates in the infrarenal zone. In this embodiment,a proximal zone 55 on the prosthesis 96 comprises a wire cage 46 but nopolymeric sleeve 44. In this embodiment, the prosthesis 96 stillaccomplishes the anchoring function across the renal arteries, yet doesnot materially interfere with renal perfusion. Thus, the polymericsleeve 44 may cover anywhere from about 50% to about 100% of the axiallength of the prosthesis 96 depending upon the desired length ofuncovered wire cage 46 such as for anchoring and/or lateral perfusionpurposes. In particular embodiments, the polymeric sleeve 44 may coverwithin the range of from about 70% to about 80%, and, in one foursegment embodiment having a single exposed segment, 75%, of the overalllength of the prosthesis 96. The uncovered wire cage 46 may reside atonly a single end of the prosthesis 96, such as for traversing the renalarteries. Alternatively, exposed portions of the wire cage 46 may beprovided at both ends of the prosthesis such as for anchoring purposes.

In a further alternative, a two part polymeric sleeve 44 is provided. Afirst distal part spans the aneurysm 40, and has a proximal end whichterminates distally of the renal arteries. A second, proximal part ofthe polymeric sleeve 44 is carried by the proximal portion of the wirecage 46 which is positioned superiorly of the renal arteries. Thisleaves an annular lateral flow path through the side wall of thevascular prosthesis 96, which can be axially aligned with the renalarteries, without regard to rotational orientation.

The axial length of the gap between the proximal and distal segments ofpolymeric sleeve 44 can be adjusted, depending upon the anticipatedcross sectional size of the ostium of the renal artery, as well as thepotential axial misalignment between the right and left renal arteries.Although the right renal artery 32 and left renal artery 34 areillustrated in FIG. 22 as being concentrically disposed on oppositesides of the abdominal aorta, the take off point for the right or leftrenal arteries from the abdominal aorta may be spaced apart along theabdominal aorta as will be familiar to those of skill in the art. Ingeneral, the diameter of the ostium of the renal artery measured in theaxial direction along the abdominal aorta falls within the range of fromabout 7 cm to about 20 cm for a typical adult patient.

Clinical and design challenges, which are satisfied by the presentinvention, include providing a sufficient seal between the upstream endof the vascular prosthesis and the arterial wall, providing a sufficientlength to span the abdominal aortic aneurysm, providing sufficient wallstrength or support across the span of the aneurysm, and providing asufficient expansion ratio, such that a minimal percutaneous axisdiameter may be utilized for introduction of the vascular prosthesis inits collapsed configuration.

Prior art procedures presently use a 7 mm introducer (18 French) whichinvolves a surgical procedure for introduction of the graft deliverydevice. In accordance with the present invention, the introductionprofile is significantly reduced. Embodiments of the present inventioncan be constructed having a 16 French or 15 French or 14 French orsmaller profile (e.g. 3-4 mm) thereby enabling placement of theendoluminal vascular prosthesis of the present invention by way of apercutaneous procedure. In addition, the endoluminal vascular prosthesisof the present invention does not require a post implantation balloondilatation, can be constructed to have minimal axial shrinkage uponradial expansion, and avoids the disadvantages associated with nitinolgrafts.

While a number of preferred embodiments of the invention and variationsthereof have been described in detail, other modifications and methodsof using and medical applications for the same will be apparent to thoseof skill in the art. Accordingly, it should be understood that variousapplications, modifications, and substitutions may be made ofequivalents without departing from the spirit of the invention or thescope of the claims.

What is claimed is:
 1. An endoluminal prosthesis, comprising: a tubularwire support comprising at least first and second axially adjacenttubular segments joined by a connector extending therebetween, whereinthe first and second tubular segments and the connector are formed froma single length of wire, and wherein each tubular segment comprises aseries of proximal and distal bends, such that each proximal bend in thefirst tubular segment aligns with a distal bend in the second tubularsegment to form a joint; wherein each joint includes an eye.
 2. Theendoluminal prosthesis of claim 1, wherein the eye is a circular loop.3. The endoluminal prosthesis of claim 2, wherein the eye is adouble-looped circular eye.
 4. The endoluminal prosthesis of claim 1,wherein the eye is a double-looped triangular eye.
 5. An endoluminalprosthesis as in claim 1, comprising at least three segments and twoconnectors.
 6. An endoluminal prosthesis as in claim 1, comprising atleast five segments and four connectors.
 7. An endoluminal prosthesis asin claim 1, wherein the wire in each segment comprises a series of strutsegments connecting the proximal bends and distal bends to form atubular segment wall.
 8. An endoluminal prosthesis as in claim 7,wherein at least some of the strut segments are substantially linear. 9.An endoluminal prosthesis as in claim 7, wherein each segment comprisesfrom about 4 proximal bends to about 12 proximal bends.
 10. Anendoluminal prosthesis as in claim 1, having at least a proximalsegment, an intermediate segment and a distal segment, wherein theprosthesis is expandable from a reduced cross section to an expandedcross section.
 11. An endoluminal prosthesis as in claim 10, wherein atleast a portion of the proximal segment and distal segment is larger incross section than the central segment when the prosthesis is in theexpanded cross section.
 12. An endoluminal prosthesis as in claim 1,further comprising a polymeric layer on the wire support.
 13. Anendoluminal prosthesis as in claim 12, wherein the layer comprises atubular PTFE sleeve surrounding at least a central portion of theprosthesis.
 14. An endoluminal prosthesis as in claim 1, wherein thefirst tubular segment has a different radial strength than the secondtubular segment.
 15. An endoluminal prosthesis as in claim 14, furthercomprising a third tubular segment, wherein at least one of the tubularsegments has a different radial strength than the other two tubularsegments.
 16. An endoluminal prosthesis as in claim 15, wherein aproximal end of the prosthesis is self expandable to a greater diameterthan a central region of the prosthesis.
 17. An endoluminal prosthesisas in claim 13, wherein the sleeve further comprises at least onelateral perfusion port extending therethrough.
 18. An endoluminalprosthesis as in claim 1, wherein the joint comprises a pivotableconnection.
 19. An endoluminal prosthesis as in claim 1, wherein thejoint comprises a metal link.
 20. An endoluminal prosthesis as in claim1, wherein the joint comprises a suture.
 21. An endoluminal prosthesisas in claim 1, wherein the prosthesis has an expansion ratio of at leastabout 1:4.
 22. An endoluminal prosthesis as in claim 21, wherein theprosthesis has an expansion ratio of at least about 1:5.
 23. Anendoluminal prosthesis as in claim 12, wherein the prosthesis has anexpanded diameter of at least about 20 mm in an unconstrained expansion,and the prosthesis is implantable using a catheter no greater than about16 French.
 24. A prosthesis as in claim 12, wherein the prosthesis hasan expanded diameter of at least about 25 mm, and is implantable on adelivery device having a diameter of no more than about 16 French. 25.An endoluminal prosthesis, comprising: a tubular wire support comprisingat least first and second axially adjacent tubular segments joined by aconnector extending therebetween, wherein the first and second tubularsegments and the connector are formed from a single length of wire, andwherein each tubular segment comprises a series of proximal and distalbends, such that each proximal bend in the first tubular segment alignswith a distal bend in the second tubular segment to form a joint;wherein each joint includes an eye in the form of a circular loop ofwire.
 26. The endoluminal prosthesis of claim 25, wherein the eye is adouble-looped triangular eye.
 27. An endoluminal prosthesis as in claim25, comprising at least three segments and two connectors.
 28. Anendoluminal prosthesis as in claim 25, comprising at least five segmentsand four connectors.
 29. An endoluminal prosthesis as in claim 25,wherein the wire in each segment comprises a series of strut segmentsconnecting the proximal bends and distal bends to form a tubular segmentwall.
 30. An endoluminal prosthesis as in claim 29, wherein at leastsome of the strut segments are substantially linear.
 31. An endoluminalprosthesis as in claim 29, wherein each segment comprises from about 4proximal bends to about 12 proximal bends.
 32. An endoluminal prosthesisas in claim 25, having at least a proximal segment, an intermediatesegment and a distal segment, wherein the prosthesis is expandable froma reduced cross section to an expanded cross section.
 33. An endoluminalprosthesis as in claim 32, wherein at least a portion of the proximalsegment and distal segment is larger in cross section than the centralsegment when the prosthesis is in the expanded cross section.
 34. Anendoluminal prosthesis as in claim 25, further comprising a polymericlayer on the wire support.
 35. An endoluminal prosthesis as in claim 34,wherein the layer comprises a tubular PTFE sleeve surrounding at least acentral portion of the prosthesis.
 36. An endoluminal prosthesis as inclaim 25, wherein the first tubular segment has a different radialstrength than the second tubular segment.
 37. An endoluminal prosthesisas in claim 36, further comprising a third tubular segment, wherein atleast one of the tubular segments has a different radial strength thanthe other two tubular segments.
 38. An endoluminal prosthesis as inclaim 37, wherein a proximal end of the prosthesis is self expandable toa greater diameter than a central region of the prosthesis.
 39. Anendoluminal prosthesis as in claim 35, wherein the sleeve furthercomprises at least one lateral perfusion port extending therethrough.40. An endoluminal prosthesis as in claim 25, wherein the jointcomprises a pivotable connection.
 41. An endoluminal prosthesis as inclaim 25, wherein the joint comprises a metal link.
 42. An endoluminalprosthesis as in claim 25, wherein the joint comprises a suture.
 43. Anendoluminal prosthesis as in claim 25, wherein the prosthesis has anexpansion ratio of at least about 1:4.
 44. An endoluminal prosthesis asin claim 43, wherein the prosthesis has an expansion ratio of at leastabout 1:5.
 45. An endoluminal prosthesis as in claim 34, wherein theprosthesis has an expanded diameter of at least about 20 mm in anunconstrained expansion, and the prosthesis is implantable using acatheter no greater than about 16 French.
 46. A prosthesis as in claim34, wherein the prosthesis has an expanded diameter of at least about 25mm, and is implantable on a delivery device having a diameter of no morethan about 16 French.